Surgical cannulae are well known in the art. Such devices generally comprise tube-like members which are inserted into openings made in the body so as to line the openings and maintain them against closure. Surgical cannulae can be used for a wide variety of purposes, and their particular construction tends to vary accordingly.
For example, some surgical cannulae are designed to serve as an irrigation passageway between the surgical site and the region outside the body. In this case, these surgical cannulae (which are sometimes referred to as "irrigation cannulae") may be little more than a hollow tube, with or without an associated stopcock.
Other surgical cannulae are designed to serve as a protective liner for the surgical opening. These surgical cannulae (which are sometimes referred to as "instrument cannulae") are used to minimize tissue trauma during the insertion, use and withdrawal of surgical instruments to and from the surgical site. Since the surgical site is typically inflated and/or irrigated with a fluid during the surgical procedure (i.e., with a liquid during arthroscopic surgery and with a gas during laparoscopic surgery), these cannulae typically include some sort of fluid seal across their central opening. This fluid seal acts to minimize fluid loss from the surgical site through the cannula. Such fluid seals typically comprise one or more soft rubber disks which extend across the cannula's central opening. These disks typically have holes or slits at their center to allow surgical instruments to pass through the fluid seal and reach the surgical site.
Prior art instrument cannulae are traditionally sold as pre-assembled and pre-sterilized units which are ready for use right out of the package. In addition, these cannulae are generally made so as to be disposable at the end of the surgical procedure. To this end, prior art instrument cannulae are typically provided with their fluid seals already assembled to the cannula housings. Since prior art instrument cannulas are intended to be discarded at the end of each procedure, their housings are generally formed out of a relatively inexpensive material such as plastic.
Prior art cannulae of the sort described above tend to suffer from a number of disadvantages.
For example, the plastic housings tend to become very slippery when wet. As a result, the cannulae can sometimes slip out of position during a surgical procedure, particularly as instruments are being passed into and out of the cannula during use.
Additionally, it is generally necessary to insert a sharp-pointed trocar into the interior passageway of the cannula during cannula insertion. This sharp-pointed trocar projects out the distal end of the cannula and serves to part the patient's tissue before the advancing cannula, as well as to prevent the cannula housing from coring the tissue during cannula insertion. Unfortunately, this sharp-pointed trocar must also be pushed through the cannula's fluid seal in order to project its sharp point out the distal end of the cannula housing. The cannula's fluid seal can be damaged by the sharp tip of the trocar as the trocar passes through the fluid seal.
Furthermore, the use of fully disposable surgical cannulae can be relatively expensive when considered in the context of the total number of cannulae used in minimally invasive surgical procedures.
It has been recognized that substantial cost savings could be achieved if some or all of the instrument cannula could be reused at the conclusion of the surgical procedure. In addition, the problem of disposing of the surgical cannula after use could also be reduced.
Unfortunately, existing surgical cannulae do not lend themselves to reuse.
For one thing, the plastic used to form the cannula housings tends to be relatively soft. As a result, the inside of the cannula housing is frequently scarred during use as sharp instruments pass back and forth through the cannula. Reuse of the same housing in subsequent surgical procedures would increase this scarring problem and could lead to small pieces of plastic becoming detached from the cannula housing and entering the patient's body.
For another thing, the fluid seal used in the cannula also tends to be scarred during use. Reusing the same fluid seal in subsequent surgical procedures could compromise the fluid seal's ability to minimize fluid loss through the cannula. In addition, reusing the fluid seals in subsequent surgical procedures would increase the scarring problem and could lead to small pieces of rubber coming loose from the fluid seal and entering the patient's body.
Furthermore, existing surgical cannulae do not provide a fast and convenient way for medical personnel to recycle only a portion of a used surgical cannula. For example, existing surgical cannulae do not provide a fast and convenient way to attach a new fluid seal to a recycled cannula housing.